This invention relates generally to a method of prolonging operation duration of ambient air heated vaporizers of cryogenic fluids.
Ambient air vaporizers have been used to convert cryogenic liquids into a warm gas for over fifty years. Because of the very cold surfaces inherent in the design of these vaporizers, they all collect frost or ice and are generally limited in the time they can be effective due to the reduction in heat transfer caused by the frozen atmospheric water collecting on the heat transfer surfaces. Operators frequently mitigate this effect by having multiple vaporizers, and alternately switching some units off, allowing them to defrost. Characteristic of these defrosting vaporizers is falling of the frost and ice off the heat transfer surfaces and collection at the base of the unit (the “Pile”). This Pile of frozen water can generally be melted by exposure to warm ambient air during the defrost situation. The Pile also can be removed manually, but this is not practical in large continuously operating installations. As arrays of vaporizers get larger to service big consumers such as steel mills or LNG receiving and send-out terminals, the number of units increase and spacing between units reduces. This precludes sufficient ambient air circulation to melt the pile. Similarly, it is not practical to remove manually the pile with large vaporizer arrays.